1. Field of the Invention
The present invention generally relates to magnetic recording media, methods of fabricating the same, and storage apparatuses, and more particularly to a magnetic recording medium which is often referred to as discrete track media, a method of fabricating such a magnetic recording medium, and a storage apparatus having such a magnetic recording medium.
2. Description of the Related Art
In storage apparatuses that are used as external storages of computers and the like, there have been rapid improvements in the recording densities of magnetic recording media. In order to achieve a high recording density, it is necessary to improve the Signal-to-Noise Ratio (SNR), and the reduction of transition noise is one of the important goals to be achieved. The transition noise depends on the size of magnetic particles forming a recording layer of the magnetic recording medium, and the smaller the magnetic particle diameter the more the transition noise can be suppressed. However, the reduction in the magnetic particle diameter causes the resistance to thermal instability of written information, that is, the thermal stability of written information, to deteriorate. For this reason, the material used to form the recording layer needs to have a high magnetic anisotropy energy, and consequently, there is a problem in that it becomes difficult for a magnetic head to write information on the magnetic recording medium.
The so-called patterned media have been proposed to avoid the problem described above. The patterned media include Discrete Track Media (DTM), Bit Patterned Media (BPM) and the like. The DTM has a structure in which the recording layer is physically isolated in a track direction. The BPM has a structure in which the recording layer is physically isolated in both the track direction and a bit direction. The DTM can improve the track density, while the BPM can improve both the track density and the line density.
As a method of forming patterns on the recording layer of the patterned medium, there is a proposed method which fabricates a stamper by the lithography technique using electron beam plotting or the like, and pushes the stamper against a resist formed on the recording layer in order to transfer patterns onto the resist. This proposed method thereafter carries out a dry etching to form the patterns on the recording layer.
The magnetic head writes information on and reads information from the patterned medium in a state where the magnetic head floats from the patterned medium by a predetermined distance. For this reason, in order to prevent damage to the magnetic head or the patterned medium due to contact between the magnetic head and the patterned medium, the medium surface of the patterned medium needs to be flat or planar. Hence, after forming the patterns on the recording layer in the manner described above, grooves of the patterns need to be filled, for example, to planarize the medium surface. A method has been proposed to fill the grooves of the patterns by a non-magnetic material such as SiO2, and to thereafter planarize the medium surface by a Chemical Mechanical Polishing (CMP).
In order to further improve the recording density of the patterned medium, it is necessary to reduce the size of the magnetic particles forming the recording layer, however, the patterned medium is easily affected by the thermal instability if the magnetic particles are small. In addition, when forming the patterns on the recording layer of the patterned medium by the etching carried out in the manner described above, portions of the magnetic particles at an etching boundary are etched to locally reduce the volume of the magnetic particles, and the patterned medium is easily affected by the thermal instability.
The applicant is aware of Japanese Laid-Open Patent Publications No. 10-125520 and No. 2008-146809.
Accordingly, there is a problem in that the conventional patterned medium is easily affected by the thermal instability because the volume of the magnetic particles forming the recording layer is locally reduced when the recording layer is patterned.